1. Technical Field
The present invention relates to a substrate for flip chip bonding and a method of fabricating the same.
2. Description of the Related Art
With the recent advancement of the electronics industry, there is a demand for increasing performance and functionality of electronic components and reducing the size thereof. Accordingly, high integration, slimness and fine circuit patterning are also required on a substrate for surface mounting components, such as SIP (System in Package), 3D package, etc.
In particular, in techniques for mounting electronic components on the surface of a substrate, a wire bonding process or a flip chip bonding process is utilized for forming an electrical connection between a semiconductor chip and a printed circuit board (PCB). In the case of the wire bonding process, because the connection of the chip to the PCB is performed using a wire, the size of a module is increased and an additional process is required. As well, limitations are imposed on realizing a circuit pattern having a fine pitch. So, the flip chip bonding process is mainly employed.
The flip chip bonding process includes forming an external connection terminal (i.e. a bump) having a size of tens of μm to hundreds of μm on a semiconductor chip using a material such as gold, solder or another metal, flipping the semiconductor chip having the bump so that the surface thereof faces the substrate, and mounting the semiconductor chip on the substrate, unlike the mounting operation based on the wire bonding.
Moreover, in order to correspond to a circuit pattern having an ultrafine pitch, the flip chip bonding process is developed to form a new structure using a metal post. The use of such a metal post is receiving attention as an alternative for achieving a fine pitch, ensuring a distance between a PCB and a semiconductor chip to thus facilitate the fabrication of a package, and improving heat dissipation performance.
FIG. 1 is a cross-sectional view showing a semiconductor substrate for flip chip bonding according to a conventional technique.
As shown in FIG. 1, the semiconductor substrate 10 for flip chip bonding according to the conventional technique includes a silicon wafer 12 having pads 14, a solder resist layer 16 formed on the silicon wafer 12 and having open portions for exposing the pads 14, metal posts 18 formed on the pads 14, and solder bumps 20 formed on the metal posts 18.
Although the semiconductor substrate 10 for flip chip bonding according to the conventional technique is evaluated to be superior in terms of height uniformity and mounting reliability, it is not easy to relieve stress applied to the metal posts 18, and thus the metal posts 18 suffer from necking defects and mounting reliability is reduced.
As well, the above metal post structure employed in the conventional semiconductor substrate has a limitation in applying it to a package substrate on which the semiconductor substrate 10 is mounted. This is because the formation of the metal posts having the same height is difficult when the metal posts are plated on the package substrate which warps in the manufacturing process unlike the silicon wafer 12.